Construct boolHook and rboolean regex to deal with boolean attributes. Fixes #9129. Fixes #9123.
- Construct regex for all attributes which are boolean attributes by specification.
+ This allows us to do what users expect with enumerated attributes and allows us to no longer complicate the issue.
+ People are just too confused with passing "true" instead of true when they should, so we won't have to worry about that anymore.
- Modularize code for dealing with boolean attributes into a separate hook to keep attr short and fast.